1. Field of the Invention
The invention relates to a friction ring for clutches or brakes, and to a method and device for producing such friction rings, the friction ring, consisting of an annular metal element with at least one cylindrical or conical friction surface comprising a spray-sintered friction lining.
2. The Prior Art
Spray-sintered friction linings have been used satisfactorily for some time in clutches and brakes, as they possess good friction properties, are durable and temperature-resistant, and can be produced relatively simply with great accuracy. In their production, the sinter powder is sprayed onto a planar support plate and then sintered on, the necessary material concentration and the required gauged thickness being attained by one or more compacting operations. Planar discs produced by this method have given particularly satisfactory results in lubricated multiple disc clutches and brakes of various types, and also, for example, in automatic change-over gears of motor vehicles and other working machines of all types.
From German Pat. No. 34 17 813 it is known, in the case of a friction clutch or brake, particularly of a synchronising device, with non-planar friction surfaces, to use a separately prepared friction element consisting of a support plate on which a friction lining has been spray-sintered and has been compacted by pressing the friction element. This separately prepared friction element is brazed or welded onto the basic element with the non-planar friction surface or is securely fixed to the friction surface in some other way. Previously, the separately prepared friction element is formed at least approximately into the shape of the friction surface and then by means of rolling, including the use of engraved rollers, is fitted onto the basic element so that it becomes friction-locked, and at least over parts of its surface, positively locked. This known friction ring is thus composed of individual parts, so that the manufacturing tolerances become added together and can negatively affect the assembly conditions and the operation. Moreover, the fitting, the matched shaping and the secure fixing of the separately prepared friction element onto the non-planar friction surfaces is relatively costly. Particular production accuracy and care are required.
A further friction ring with a spray-sintered friction lining is known from British Pat. No. 1 325 304. In this, a cylindrically-shaped brake band, open in a circumferential position, is provided with a brake lining consisting of a support in the form of a flexible steel plate with a spray-sintered friction lining thereon and fixed to the brake band by spot welding. This known execution also uses a separately prepared friction element, and therefore conforms substantially to the friction clutch or brake described in German Pat. No. 34 17 813, and the same cost and care are involved in its production.
In the brake band described in British Pat. No. 1 325 304, the spray-sintered friction lining can be formed on the support plate either as a continuous layer or as spaced-apart portions of sintered friction material. These portions can be formed slightly curved during the sintering operation, so that the cylindrical shaping of the overall friction lining for its fitting on to the brake band can be done without difficulty. U.S. Pat. No. 2,793,427 also describes a separately prepared friction element for the same purpose, in which slots are formed in a spray-sintered friction lining on a support plate during the actual production thereof, for example by using a compacting plunger provided with ribs, the friction lining being simultaneously divided into portions so that the subsequent shaping of the friction lining into a non-plane friction surface is made easier.
Finally, German Patent Document No. 34 12 779 describes a method for producing a synchronising ring from a composite material, in which the metal layer forming the friction cone is bonded to a protective layer formed from another material. In this known method, circular shapes are firstly punched out of a composite material in the form of a steel-aluminium alloy strip, and these are then shaped into synchronising rings by a non-cutting shaping method, for example by stamping, deep-drawing or the like. In this case no spray-sintered friction lining is provided. The friction lining consists on the contrary of an aluminium alloy which is in combination with the annular element forming the support part as a composite material. This composite material is shaped by a non-cutting process into a friction ring with a cylindrical or conical friction surface, to form the synchronising ring.